Typical wiper blades used on vehicles are plagued with numerous persistent drawbacks. Among these drawbacks are two common and interrelated drawbacks are of interest. The first such drawback is wiper blade separation from the surface of the windshield. The second such drawback is wind noise generated by the air moving over the wiper blade as a vehicle travels at speed.
One persistent cause of wiper blade separation from the windshield is the lack of sufficient downward force from the wiper blade onto the windshield. A major contributing factor to insufficient downward force involves wind lift. That is, wind passing over the windshield creates a “lifting” force which may cause the wiper blade to lose partial or complete contact with the surface of the windshield, and thus result in uneven or inconsistent clearing of water off the windshield. The wind lift problem has been known in the wiper field for decades, and many attempts have been made to resolve it. For example, see U.S. Pat. Nos. 3,056,991, 3,317,945, 3,879,793, 3,942,212, 6,292,974, 6,944,905, which are incorporated herein by reference in their entirety.
One common solution to the wind lift problem is to add a wind deflection structure, or spoiler, to the top of the wiper blade. On a beam blade, a spoiler is generally affixed to the top of the wiper blade, thereby substantially increasing the height and outer cross-section of the wiper blade overall, and increasing the need for an anti wind-lift structure. Moreover, for cost and ease of manufacture reasons, these spoilers have a uniform cross-sectional profile across the entire length, or substantially the entire length of the wiper blade structure. U.S. Pat. No. 6,944,905, for instance describes a uniformly shaped spoiler, except for the end sections, in which a wall and abrupt corner are used at the end of the wind deflection strip, slanting down to the end of the blade.
Another problem associated with wiper blades is that wind noise generated as a wiper blade is used while the vehicle travels at higher speeds. In general, undesirable wind noise from wiper blades originates in part from air vortices formed by wind contacting a wiper blade. In normal operation, as wind flows over a wiper blade, an air vortex forms behind the wiper blade, that is, on the leeward side of the wiper blade. Moreover, the size of the vortex is proportional to the height of the wiper blade, from its contact point with the windshield to the top of its cross-sectional profile. Thus, a wiper blade with a larger wind deflection structure generates a larger vortex, and therefore more noise.
Generally, wind noise is created as a wiper blade enters a slip stream of wind above the windshield. The wind noise created from wiper blades encountering the slip stream is distracting and makes for a less comfortable overall driving experience. Reduction of such wind noise is therefore a constant concern associated with wiper blade design.
Wiper blade separation from the windshield is a primary concern in wiper blade design because of potential safety hazards that can arise out of poor wiping performance. However, a wiper blade designer should also attempt to minimize the amount of noise caused by the design of the wiper blade in order to allow for a more comfortable driving experience for the driver of the car on which the wiper blades are installed. Wiper blades currently used in the art do not adequately present a solution that addresses the wind lift problem while minimizing the amount of noise generated by the wiper blade.